The present application relates to a method and system to colorize three-dimensional models produced by a printing or layering process. This process is performed when a solid imaging or model building printer, such as a thermojet printer, is supplied with computed aided design data for generating a rapid prototype of a part.
Current solid imaging printers, such as the Thermojet from 3D Systems, Inc., create solid models from computer aided design (CAD) data generally according to the following steps:
Step 1. The CAD data is converted to an industry standard stereolithography (STL) data format.
Step 2. The data for the model represented by the STL file is used to determine data representations of thin (e.g., 0.001 inch) cross sectional layers of the model.
Step 3. Each of the cross sections is converted into a bitmap.
Step 4. Each bitmap is printed onto a platform successively one on top of another for progressively building the model.
Step 5. The resulting model is removed from the platform.
Full color (two dimensional) printing on a planar substrate is traditionally achieved by a four color process method whereby ink for each of the primary colors such as cyan, magenta, yellow, and black, are applied to the substrate in specified or predetermined percentages to produce each desired color of a spectrum of colors. More particularly, such color printing uses 2 to 6 grayscale renderings of the same image in combination, wherein each grayscale image is printed with a different primary color, and it is the combination of these primary colors that gives the appearance of all other colors. In particular, the primary colors may be applied in layers to the planar substrate as needed to achieve the desired coloring. However, there has been no comparable process of printing for colorizing a three-dimensional model generated by, for example, an extrusion process, such as the five step process above that is used with solid imaging printers. In particular, providing full color to such three-dimensional models has previously been performed by applying decals or painting such resulting models after they have been constructed.
The reasons for coloring a three-dimensional model after construction has been at least due to difficulties of manufacture (i.e., the computational complexity of rendering a full spectrum of colors in three dimensions, and the complexity of providing variously colorized model building materials to such a solid imaging printer). For example, an impediment to colorizing three-dimensional model during model generation has been the belief that duplicate substrate delivery systems (one for each primary colored substrate) would be required when building colored models. Accordingly, such duplication would likely require additional heating or melting components, and additional substrate reservoirs. Moreover, such difficulties have previously inhibited development of a process similar to the two dimensional printing process for use in the generation of three-dimensional models. Previously, the contemplated modifications to, for example, the thermojet machine to produce colored three-dimensional models during model construction have been cost prohibitive both by reason of cost to manufacture the models as well as cost of machine operation when compared to the one color rapid prototyping (RP) methods and machines currently being used (in conjunction with, for example, a subsequent step of model painting).
With traditional two dimensional color printing four colored inks (e.g., cyan, magenta, yellow, and black) have been combined to produce a full spectrum of colors. With three-dimensional printing, a fifth model building material (herein also referred to as the xe2x80x9csubstratexe2x80x9d, or xe2x80x9ccenter portionxe2x80x9d of a three-dimensional model) is also required to be output (i.e., jetted or sprayed) from the solid imaging printer together with the four primary colors in order for the printer to build the internal structure of the model at the same time that it is applying color to, for example, a relatively thin model thickness (or shell) at the surface of the model. Accordingly, in one naive application of the two dimensional color printing approach to three-dimensional printed models, the printhead assembly for such a solid imaging printer must include at least five printheads: one printhead for each of the four print colors and at least one printhead to output the model building material that provides the bulk of the resulting model. While this is entirely possible, most printhead assemblies of such imaging printers are designed to jet, at most, four different materials. Thus, to jet five different materials increases the complexity of such a three-dimensional imaging printer in terms of size, electronics, material delivery as well as computational complexity and other factors all of which increase the cost of such a machine. Moreover, there is likely increased maintenance and lowered reliability with the additional complexity of an extra printhead. Additionally, the prospect of cost effectively retrofitting currently available four printhead solid imaging printers with a five printheads is unlikely.
Accordingly, it would be desirable to have a method and system for cost effectively colorizing a three-dimensional model as it is being constructed by, for example, a solid imaging printer. Moreover, it would be particularly desirable to have such a method and system, wherein currently available solid imaging printers that generate three-dimensional models in a single color (or colorless) can be easily retrofitted to additionally produce colored three-dimensional models.
The drawbacks and disadvantages of the prior art are overcome by the three-dimensional model colorization during model construction from computer aided design (CAD) data.
The present application discloses a method and system for coloring a three-dimensional model as it is being constructed by an extrusion process such as is performed by a thermojet printer or other solid imaging printer. In particular, the present application discloses a method and system for coloring the surface of such an extruded model during its construction.
The method and system of the present application may be implemented with a new solid imaging printing machine. However, in an alternative embodiment (and at least in some contexts a preferred embodiment), the present invention may be performed by retrofitting currently available solid imaging printing machines so that with minimal changes or additions, full color three-dimensional models may be printed (e.g., extruded). For example, in one embodiment that is compatible with the retrofitting of currently available imaging printers, a traditional printhead assembly having a four printhead array of jets is utilized. Currently available imaging printers, such as the Thermojet machine from 3D Systems Inc., utilize such a printhead assembly. However, the four jet arrays are used as a single large array to jet a single colored (or colorless) model building material through the combined jet arrays. The present application utilizes a greater degree of the functionality of such printhead assemblies (with, perhaps, minor enhancements thereto) to generate colorized three-dimensional models.
Moreover, in retrofitting of available solid imaging printing machines consideration is given to keeping color printing production costs of such three-dimensional models low, as well as keeping low the amount of time required to retrofit the currently available solid imaging printing machines.
Additionally, to keep the overhead low for implementing new training and maintenance procedures of field engineers already familiar with existing solid imaging printing machines. Accordingly, in a first embodiment, a combination of software and hardware modifications or add-ons (rather than a total redesign) as a retrofit is provided herein. Moreover, the modifications to existing solid imaging printing machine hardware are minor. In particular, such a printer will continue to function as a xe2x80x9cdumbxe2x80x9d printer, in that it is unnecessary that the imaging printer distinguish between colors.
Furthermore, the modifications to the software to provide the present invention in an existing solid imaging printer is also minor. For example, the software of a data model preparation module (e.g., a module, possibly remotely linked to the solid imaging printer via a network such as the Internet, wherein the module prepares STL data files for input to the printer) does not need to make distinctions between colors. That is, since currently available imaging printers are able to print many STL models simultaneously without knowledge of colors, such simultaneous model printing can be used to build color models by simultaneously building the following four xe2x80x9csub-modelsxe2x80x9d:
(a) a model corresponding to most of the interior of the color model;
(b) a model corresponding to grayscale rendering of the amount (i.e., number of layers) of cyan to be layered at the surface of the color model (the darker the grayscale, the more surface layers of cyan);
(c) a model corresponding to grayscale rendering of the amount (i.e., number of layers) of magenta to be layered at the surface of the color model (the darker the grayscale, the more surface layers of magenta); and
(d) a model corresponding to grayscale rendering of the amount (i.e., number of layers) of yellow to be layered at the surface of the color model (the darker the grayscale, the more surface layers of yellow).
Thus, if such an imaging printer is sent an STL data file describing each of these four sub-models for simultaneously printing, the imaging printer will print (i.e., build) each sub-model simultaneously on the printer platform thereby resulting in the color model being built. Accordingly, a modified embodiment of a currently available imaging printer will continue to print a model, or several models simultaneously. However, for building a color model, each sub-model will be printed through a predetermined different jet array of the imaging printer. Therefore, a new and/or retrofitted solid imaging will simultaneously print all four sub-models (e.g., three grayscale sub-models of the color model and a non-colored interior sub-model of the colored model), but the sub-models will be printed in the same space on the printing platform of the printer.
Thus, the primary software modification necessary for implementing the present invention with a currently available solid imaging printer is a modification to the CAD software so that each of the above described sub-models are represented in, for example, a different STL data file prior to exporting these files to the imaging printer. Therefore, the main modification to the software for retrofitting the present invention to use current printers is an addition and/or enhancement of a pre-processing module to obtain the STL files of the sub-models prior to activating such a printer. In particular, this pre-processing module identifies and separates portions of an image by color at the CAD software workstation as an export filter prior to the creation of an STL file. The four STL files output by the color export filter will have no color information included in them, just as two dimensional color separations have no color information included in them.
It is also an aspect of the present invention that together with at least one of four sub-model STL files, a descriptor or other identification may be exported indicating which sub-model file corresponds to which primary color. Alternatively, predetermined file naming conventions may be used for identifying the color to be used in rendering each sub-model STL file.
Thus, at a high level (and as will be explained more fully in the Detailed Description herein), the following steps are performed by the present invention:
(a) Separate the color data of a full color object, texture map, three-dimensional color scan, etc. into three primary colors and create separate xe2x80x9cshell objectsxe2x80x9d of the primary colors. Shells would be preferred rather than solid objects, as the interior of the color is not needed and the amount of material needed to print a shell is greatly reduced.
(b) Send (or transfer) the shell object data and the primary substrate object data to the printing machine in the same manner as is currently performed, with the main difference being to send each object to a separate printhead, and build the object in the same fashion as is currently performed, with the exception being to build each object in the same three-dimensional space rather than four separate spaces.